If you are signing Grandal, the motivation for Moustakas is far lower because you've found yourself LH hitting, middle of the order help, and you still have RF where you can add another LH bat if you're really after balance. If you sign Grandal and still want a DH, now you're in a much stronger place to go after Castellanos or Encarnacion (or trade for Martinez). You may as well hold onto Sanchez or pick up some other bench option (maybe one who can be a stronger backup SS like Iglesias) rather than going after Moustakas in that case.
The downside of that set of moves, IMO, is that it leaves me fewer resources to spend on the pitching staff, which is still the way I'd handle this.